The present invention relates generally to capotasto devices for varying the resonant length of tensioned strings on stringed musical instruments such as a dobro, banjo, Hawaiian guitar, or the like. More particularly, this invention relates to a unitary, self-locking capo device which firmly engages the strings of the instrument operatively independently of the neck of the instrument. The invention is believed to be classified in U.S. Class 84, Subclass, 318.
The typical dobro is somewhat similar in appearance to a standard or classical guitar, and generally comprises a hollow body portion with a metallic acoustic panel, an elongated neck portion, which terminates in a tuning head, and six tensioned strings which are tuned to an open G-major chord. Typically, dobro strings are comprised of heavier gauge wire than standard guitar strings and are therefore substantially less flexible. More importantly, the strings of the typical dobro are positioned well above the fretboard on the neck of the instrument, so that the distance between the dobro string the the fretboard is much greater on a dobro than on a standard guitar. Moreover, the neck of the dobro is wider than the neck of a standard guitar. The dobro is generally held in a "flat" position across the lap of the player or on a strap, so that the neck and strings of the instrument are horizontal, approximately perpendicular to the player's body.
The skilled player does not finger the individual strings of the dobro to form a desired chord, but simply dampens or compresses various strings with a solid slide or similar bar at the appropriate position across a fret with one hand while strumming or plucking the strings with the other hand. The dobro is typically tuned to an "open tuning", which means that a major chord (usually G major) is played when all the strings are strummed together. As will be appreciated by skilled musicians familiar with the dobro or similar stringed folk instruments, a capo device is frequently desired in order to vary the pitch of the instrument when a change of key is desired for a particular song.
A number of prior art capo devices have been introduced which are suitable for use with a standard guitar. Generally, such prior art capos lockingly engage about the circumference of the neck and compress the guitar strings to the fretboard at the desired fret position.
One representative prior art guitar capo is disclosed by Myerson et al., U.S. Pat. No. 4,252,046, issued Feb. 24, 1981. The device includes a flexible, elastic band which encircles the neck of the guitar and can be selectively tensioned to engage a rigid shaft to compress the strings to the fretboard. Similar flexible bands are employed in capos described in U.S. Pat. No. 1,788,636, issued to Russell on Jan. 13, 1931; Wowries, U.S. Pat. No. 3,504,589, issued Apr. 7, 1970; U.S. Pat. No. 3,933,077, issued Jan. 20, 1976 to Dunlop; and, Labbe, U.S. Pat. No. 4,503,747.
Another type of adjustable prior art guitar capo is shown in U.S. Pat. No. 4,250,790, which comprises a rigid jaw member which clamps about the neck and strings of the instrument and is adjusted by means of a screw. Similarly screw-adjustable capos are found in U.S. Pat. Nos. 3,933,073; 4,324,165; 4,270,432; and 4,104,947. A number of rigid, pivotally clamping capos are also known in the prior art, of which U.S. Pat. Nos. 4,143,576; 4,149,443; and 4,583,440 are representative.
None of the prior art capos known to me, however, is of particular value to the dobro player. Because the neck of the dobro is generally wider than the neck of a standard guitar, it is difficult to fit a guitar capo to the dobro. Also, since the strings of the dobro are positioned at a substantially greater distance above the fretboard than they would be on the guitar, it is impractical if not impossible to "capo" a dobro by pressing the string down into contact with a fret upon the fret board.
The most obvious disadvantage of using a typical guitar capo for a dobro is that the sound produced when the capo is in place is not "true". The object of using a capo is to most closely approximate the sound produced when an "open" chord is played. If the strings of a dobro were to be tightly clamped against the fretboard, the natural resonance and resilience of the strings would be greatly reduced. Thus, the sound is greatly dampened and, particularly, the unique bass tones produced by the dobro in open tuning would be lost.
Another major disadvantage is encountered with the placement of the conventional guitar capo on the dobro neck. Typically, the adjustment nut or some portion of the guitar capo extends above the surface of the strings and/or to the side of the neck. When the skilled dobro player attempts to maneuver the slide bar along the horizontal surface of the dobro strings to form a desired chord, the capo structure will interfere with the player's hand or arm movement. This is particularly vexatious when the desired chord is formed closed to the capo.
It is therefore desirable to provide a capo which is adapted to be compressively fitted directly upon the strings of the dobro to permit the full natural resonance of the strings and to minimize interference with the player's hand and arm movements.
Some suggestion for so compressing the strings of an instrument independent of the neck is made by Ito in U.S. Pat. No. 3,971,287, issued July 27, 1976. The sound dampening device described therein comprises a pair of rigid, cooperating hinge portions lined with a resilient, spongy material to reduce the natural resilience of the strings. No suggestion is made therein as to the possible advantage of effectuating a key change by selective placement of the device relative to the fretboard.